Increased detection of sentinel nodes in breast cancer patients with the use of superparamagnetic iron oxide tracer.

Abstract

100 Background: The use of superparamagnetic iron oxide (SPIO) tracer for sentinel node biopsy (SLN) has shown non inferiority compared with the radioisotope technique in early breast cancer. False negative rates of SLN biopsy after neoadjuvant treatment (NAC) have decreased with dual tracer (radioisotope/dye) and with the excision of > 2 SLNs. This study was designed to evaluate the outcome of SLN after NAC using a dual tracer (SPIO-Tc99) and to compare it with the SLN by same dual tracer in the adjuvant setting. Methods: Between July 2013 and March 2014, 30 patients with invasive breast cancer (IBC) and SLN biopsy after NAC (NAC- SLN), and 118 patients with IBC not treated with NAC (adjuvant SLN), whose SLN was traced by Tc99 and SPIO were included in the study. Patients were injected subareolar with Tc99 the day before surgery and with the SPIO intraoperatively. SLN was excised if it was radioactive, magnetic or palpable. Patients signed an inform consent. Results: Detection rate by Tc 99 was successful in 113 (95.7%) patients and by SPIO in 116 (98.3%) in the adjuvant SLN (P= 0.0833) while in the NAC-SLN group detection rate by Tc-99 was successful in 28 patients (93.3%) and by SPIO in 30 patients (100%) (P =0.1573). Concordance rates per patient in the adjuvant SLN between techniques was 98.2%, while in the NAC-SLN was 100%. (p = 0.4762) Mean number of SLNs excised by 99Tc and SPIO were 1.9 and 2.21 respectively in the adjuvant SLN, (p=0.001) while 1.533 and 2.60 respectively in the NAC-SLN group. (p=0.0016) In the adjuvant SLN, the SLN was positive in 36 patients (30%), and in the NAC-SLN in 9 patients (30%). In the adjuvant SLN, both techniques detected same number of positive nodes but in the NAC-SLN, 9 patients had a positive SLN by SPIO (> 2 SLNs by SPIO and 1 SLN by Tc99) and 7 patients had a positive SLN by Tc99. Conclusions: Detection of SLNs with SPIO allows for easy identification of axillary nodes and can be used to reliably identify SLNs in breast cancer. Even though the small sample size in the NAC-SLN, the higher number of SLNs excised by the SPIO may optimize the success of SLN after NAC.